4.5 Archaeoentomology in Scotland: Background and Potential

Archaeoentomology is the area of Quaternary Entomology which deals with insects from archaeological contexts. These range from reconstructions of natural and anthropogenic contexts to reconstructions of climate. Application of the technique depends on anaerobic preservation which is optimal in permafrost, very wet and very dry environments (Buckland et al. 2004). Occasionally, insect remains can also be preserved by mineralisation and charring. Insects are the most abundant animals and their study involves different categories. Beetles (Coleoptera), flies (Diptera) including Chironomidae, and other groups as for example Hemiptera (bugs), Orthoptera (grasshoppers), Siphonaptera (fleas) and Anoplura (lice) are all frequently found in archaeological deposits. As the number of species is immense, study is dependant on the state of taxonomy for each group. For some groups larval and pupal stages have yet to be described and work has therefore concentrated upon the adult stage, particularly of beetles.

Insects from archaeological sites are recovered from soil samples retrieved from suitable contexts during the excavation. In Northern Europe, samples of particular interest are from areas in the excavation with organic preservation, in particular floors, middens, storerooms, drains and there is little point in a random sampling technique. The ideal sample size is 5 litres, however smaller or larger samples can be examined depending on context and availability. Columns of samples, taken in 100mm slices with due regard to stratigraphic boundaries, from peaty or other organic deposits nearby the site can provide an understanding of surrounding environments. For samples taken from waterlogged deposits the technique used for concentrating insect remains is paraffin flotation (Coope 1986). The float is then examined under a stereomicroscope, sorted for entomological material and then examined using a comparative collection. In the case of Chironomidae, their high frequency in lacustrine sediments dictates much smaller and closer interval sampling and significant faunas may be recovered from 1cc of sediment (cf. Brooks 2006).

The Coleoptera, beetles, may be very sensitive indicators of change and many species have particular habitat and temperature requirements. They are used, for example, to provide data on climate change, changes in woodland frequency or its character, changes in the nature of a settlement, human activity and trade, health, hygiene, death and decay (Buckland et al. 2004b). Diptera, true flies, in particular their pupae and puparia are usually closely related to the contexts in which they have bred, and provide immediate information on these environments, often with an emphasis on the forensic aspect of the research where appropriate (Panagiotakopulu 2004). Chironomidae, non biting midges and Simuliidae, the blackflies, are indicative of water quality, and their sensitivity to change makes them excellent indicators of both degree of eutrophication and climate change (Brooks 2006). the caddis flies, Trichoptera, are also found in lake and river sediments (Greenwood et al. 2006) and Acarina, mites, may be useful indicators of a variety of man-made habitats, particularly dung (Schelvis 1997). The ectoparasites (e.g. Anoplura (lice), Cimicidae (bed bugs), Siphonaptera (fleas) and keds (Diptera, Hippoboscidae), may be host specific and frequently spend their entire life cycle on their hosts, so they can be used to indicate presence of humans and animals, hygiene conditions, disease and trade (Panagiotakopulu 2001, Panagiotakopulu 2004b). The BUGScep database includes an extensive entomological bibliography, the fossil archive, including all published Scottish records, and information on habitat and distribution of Coleoptera (Buckland and Buckland 2006).

Fossil insect studies from Scotland are largely restricted to beetles and a few studies of Diptera. There are a few studies from both the Western and Northern Isles (e.g. Roper 1999; Buckland 1999; Skidmore 1996) but, apart from extensive studies in urban Aberdeen (Kenward and Hall 2001) and of the crannog at Buiston (Kenward et al. 2000; Skidmore 2000), work from the mainland is scarce. In the broader context, Buckland and Sadler (1997) summarise palaeoentomological studies from Scotland including a discussion of extinctions and introductions of species from the Lateglacial onwards, although this is in need of updating. Lateglacial faunas from several sites in Dumfrieshire (Bishop and Coope 1977), Corstophine and Saughton on the edge of Edinburgh (Coope 1968) and Burnhead in Lanarkshire (Coope 1962) have demonstrated the potential of Coleoptera as climatic indicators, marking the changing climate during the Late Glacial. A more detailed picture of Holocene change is presented by chironomid assemblages from sites in the Cairngorms (e.g. Battarbee et al. 2001) and a succession from Whitrig Bog, near Kelso in the Borders (Brooks and Birks 2000), where the succession has also been collated with the Icelandic tephra sequence (Pyne-O’Donnell et al. 2008).

Studies from Red Moss in northeast Scotland (Clark 2003), where beetle and pollen evidence were brought to bear on the Elm Decline (Clark and Edwards 2004), and the Outer Hebrides (Dinnin 1996, Buckland and Dinnin 1993) show the decline of forest faunas as a result of clearance during the Late Holocene. The transition to an agropastoral economy seems apparent in the insect faunal assemblages from Skara Brae (Sadler 1993, Buckland and Sadler 1997), although this is less clear in the case of Knap of Howar (Kenward 1983), also on Orkney. Warsop (2000) and Skidmore have also examined small faunas from the Neolithic site at Eilean Domhnuill a Spionnaidh on North Uist.

From the foreshore next to the broch at Dun Vulan on South Uist, Roper (1999) recovered extensive dung and fodder fauna as well as a littoral one. The dispersal of storage pests to the outermost reaches of the Empire during the Roman period are indicated by the fauna from faecal material in the ditch at Bearsden on the Antonine Wall ( Dickson et al. 1979). The Buiston Crannog deposits of Late to post-Roman date (Kenward et al. 2000; Skidmore 2000) represent the most extensive study so far undertaken and point the way towards the potential of insect fossils for site interpretation. Assemblages from several Norse sites on the Northern Isles have been related to studies of Viking colonisation in reference to more extensive studies from the North Atlantic islands (cf. Sadler 1993; Sadler and Buckland 1998). Later medieval sites include a pit adjacent to a monastery at Pluscarden Priory, near Elgin (Buckland 1995; Skidmore 1995), urban deposits in Aberdeen and Inverness (Smith 2002), burials in Glasgow Cathedral (Buckland 2002), and a garderobe at Carrick Castyle in Argyll (Warsop and Skidmore 1998) and these serve to demonstrate the range of information from health, hygiene and economy to forensic science. The use of analogues for archaeological record has also been highlighted with entomological work from abandoned Hebridean blackhouses (Smith 1996), and there is a clear need for more taphonomic studies.

The potential for palaeoentomological data from Scotland to detail the rapid climatic transition from the Lateglacial to the Holocene (cf. Brooks and Birks 2000) and the more subtle climate changes during the Holocene is great, and could be used, for example, to examine the putative effects of climate change on human settlement during the Bronze Age, when there are extensive shifts in cultivation limits and upland settlement, the reasons for which are disputed (cf. Buckland et al. 1996). Changes in the forest, extent of pastoralism compared with arable, introductions of faunas as a result of trade with Roman and Norse expansion, urbanisation and history of disease are all areas for exploration using insect remains and a combination of the various branches of archaeoentomology. Obtaining a good understanding of development of insect assemblages in relation to expanding patterns of human occupation will not only provide answers to archaeological questions, but will also give a new outlook for future considerations concerning environmental change and conservation.

Quaternary entomology is taught in Scottish (Edinburgh), English (York, Birmingham, Oxford, Royal Holloway) and Irish (Belfast) Universities, and several researchers work based in Museums (e.g. BMNH) and in association with archaeological consultancy Units. Insect collections are housed in Edinburgh GeoSciences, Birmingham Archaeology and Oxford Archaeology. A list of publications in Quaternary Entomology, Qbib is available at (http://www.bugscep.com/qbib.html) and a database archiving all existing work in archaeoentology is also web based: www.BugsCep.com.